One part of the answer would certainly be material conditions. It's easy to support socialism when it has given you a job and a place to live, but since "reunification", vast parts of the economy were dismantled and the free market was unleashed, leading to widespread poverty, brain drain, all the good stuff. And it seems to me that poverty leading people to support fascism always wins out over having received an anti-fascist education, unfortunately. Still, the Left is more popular in the East than the West, but who knows if it's due to the legacy of socialism or just because of regional differences within the party.